One or more aspects of example embodiments of the present disclosure are related to a material for an organic electroluminescent device and an organic electroluminescent device including the same. Aspects of the present disclosure are related to a hole transport material for an organic electroluminescent device with high emission efficiency and a long lifetime, and an organic electroluminescent device including the same.
Organic electroluminescent (EL) displays have been actively developed in recent years. Unlike liquid crystal displays (LCDs) and the like, organic EL displays are so-called self-emitting type (e.g., “self-emitting” or “self-luminescent”) displays, in which holes and electrons are respectively injected from an anode and a cathode into an emission layer, where they recombine and cause light emission by a luminescent material (including an organic compound) included in the emission layer, thereby displaying images.
An example organic EL device may include an anode, a hole transport layer on the anode, an emission layer on the hole transport layer, an electron transport layer on the emission layer, and a cathode on the electron transport layer. Holes from the anode may be injected via the hole transport layer into the emission layer. Electrons from the cathode may be injected via the electron transport layer into the emission layer. The holes and the electrons injected into the emission layer may recombine to generate excitons in the emission layer. The organic EL device emits light using energy generated by radiation deactivation (e.g., radiative decay) of the excitons. The organic EL device is not limited to the aforementioned configuration, and many modifications thereof are possible.
Display applications require organic EL devices having high efficiencies and long lifetimes. Organic EL devices in the blue light emission region require high driving voltages, and may therefore suffer from low emission efficiencies compared to organic EL devices in the green and red light emission regions. Ongoing strategies for achieving organic EL devices with high efficiencies include normalization, stabilization, and increasing the durability of a hole transport layer.
Various aromatic amine compounds have been used as hole transport materials in the hole transport layers of organic EL devices in the related art. However, further improvements in the emission efficiency of a device are desired. A diamine derivative has been suggested as a favorable material for increasing the emission efficiency of an organic EL device in the blue light emission region. A triamine derivative having three amine moieties has also been suggested in the related art. However, because the ionization potential of each of these compounds is too low, and the energy gap of each of these compounds is too small, organic EL devices in the related art that use these compounds may still be affected by limitations including the loss of recombined excitons, etc. For example, when a hole transport layer containing the triamine derivative is adjacent to an emission layer, the efficiency of the device may still be deteriorated due to transfer of excited energy (e.g., excitons) from the emission layer. Accordingly, an organic EL device having even higher efficiency is required.